Neurobehavioral toxicity in progeny of rat mothers exposed to methylmercury during gestation.

INTRODUCTION: Methylmercury (MeHg) is recognized as one of the most hazardous environmental pollutants. This may be a concern to long-term consumption of contaminated fish and seafood for health risk to pregnant women and their children. AIM: An animal study was conducted to assess the effect of MeHg exposure on rodent offspring following in utero exposure. METHODS: Pregnant Wister rats were treated by gavage with MeHg at dose levels of 0.5, 1.0 and 2.0 mg/kg/day from gestation day (GD) 5 till parturition, and then were allowed to deliver. RESULTS: Dams treated with 2.0 mg/kg/day MeHg group showed signs of toxicity such as gait alterations and hyperactivity resulting in the failure to deliver sustainable viable pups. MeHg had significant effects on body weight gain of dams during GD 5 till parturition. MeHg had no significant effects on the ages of physical developments such as pinna detachment, incisor eruptions or eye opening as well as alter cliff avoidance, surface righting, swimming ontogeny, startle reflex, pivoting, negative geotaxis, or forelimb and hindlimb grip strength in either sex. Exposure to 1.0 mg/kg/day MeHg treatment group prolonged gestation period, retard mid-air righting in male pups, shortened forelimb grip strength measured on rotating rod in either sex and enhanced open field behaviour in male pups. Data obtained from Functional Observation Battery (FOB) also revealed impairment of neuromotor performance in male pups. The male pups appeared to be more susceptible than the female pups. CONCLUSION: Overall, the dose level of MeHg in the present study produced a few adverse effects on the neurobehavioral parameters, and it may alter neuromotor performance of the male pups.

Influence of gestational exposure on the effects of prenatal exposure to methyl mercury on postnatal development in rats.

Fish and other aquatic organisms are important source of dietary proteins for the human population. Fish meat, however, is contaminated with methyl mercury (MeHg), a potent neurotoxin. The well known Minamata and Niigata epidemic outcomes in Japan have raised the awareness of the health risk resulting from consumption of fish (and shellfish) from water basins polluted with industrial wastes containing mercury. In the present study, pregnant rat dams were exposed to environmental toxic elements--methyl mercury, 1000-1200 h, daily from the fifth gestation day (GD5) till parturition. Three groups of animals were given, by gavages, MeHg (0.5, 1.0 and 2.0 mg/kg/day) and control group received 0.9% saline at the same time. All animals were allowed to deliver and wean their offspring. Pups were evaluated for early development effects. There was a significant effect of treatment on somatic growth such as reduction in percentage of maternal weight gain (20.62%) at higher dose level whereas there was no change in percentage of live birth (100.00%) with 0.5 and 1.0 mg/kg dose treatment groups. There was a significant increase in the percentage of resorption (100.00%) per litter with 2.0 mg/kg/day MeHg dose. Average gestation length (days) and percentage resorption per litter or percentage foetuses/malformations per litter were not affected at 0.5 and 1.0 mg/kg/day dose level. The results of the study confirmed the high-teratogenic potential of MeHg and the need of payng increased attention to MeHg concerning its exogenous use during pregnancy.